Gas combustion-control method and gas combustion device

ABSTRACT

A gas combustion device  1  comprises a combustor  11  for burning fuel gas supplied from a gas source, an air blower  15  for adjusting the amount of air in a cylindrical casing  5  which contains the combustor  11  therein; an ejector  7  with a primary air hole  37  for sucking a primary air into a gas passage leading from the gas source to the combustor  11  due to negative pressure caused by flow rate of the fuel gas supplied to the combustor  11  and an ignition device  9  for igniting mixed gas injected from a wick  39  provided ahead of the ejector  7.  When fire is set to the mixed gas of the wick  39,  ignitability of the mixed gas is improved by decreasing the amount of air in the casing. After ignition, combustion is maintained in the state where combustibility of the combustion gas in the combustor  11  is improved by increasing the amount of air in the casing  5.

TECHNICAL FIELD

The present invention relates to a gas combustion device for generating completely burnt hot air or warm air using burning flame by, in particular, Liquefied Petroleum Gas (LPG) as a heat source.

BACKGROUND ART

A gas combustion device has been conventionally installed in devices such as portable hair driers and heat guns using LPG.

Referring to FIGS. 1 to 4, in a gas combustion device 103 installed in a hair drier 101, for example, a combustor 105 for burning gas is provided in a cylindrical casing 107 of the hair drier 101. The combustor 105 burns fuel gas supplied from a gas tank (not shown) as a gas source and air heated by the combustor 105 is flown to the side of a vent 117 by an air blower 115 comprised of a motor 111 provided at the side of an inlet of the casing 107 via a bracket 109 and a fan 113 attached to the motor 111.

An ejector 123 with a suction port 121 for sucking outside air due to negative pressure caused by a flow rate of the fuel gas supplied to the combustor 105 is provided in a gas passage 119 leading from the gas tank to the combustor 105. As shown in FIG. 3, supplied LPG, for example, is injected from a nozzle 125 in the ejector 123 at high speed. Negative pressure occurs due to the ejector effect caused by the injection speed of gas and outside air necessary for combustion is flown into the ejector 123 from the suction port 121 to generate mixed gas consisting of LPG (gas) and air.

The mixed gas is injected a wick (metal mesh) 127 provided within the combustor 105 at the side of its inlet and a spark generated from a ignition plug (ignition device) 129 through high-tension electricity is blown to the wick 127 and ignites the injected mixed gas.

The combustor 105 is disposed between the air blower 115 and the vent 117 of the casing 107. Apparent from the shape of a cross section perpendicular to the longitudinal direction of the combustor 105 shown in FIG. 4, the combustor 105 is a non-circular cylindrical body in which the wick 127 is centrally located which has eight radial groove-like combustion chambers 131 in the shape of eight-divided star-like projections around the wick 127 (refer to Japanese Patent Application Laid-Open Publication No. 2002-233416).

As shown in FIG. 1, in a state where the amount of air sent from the air blower 115 is constant, a process of igniting and burning the fuel gas using the conventional gas combustion device comprises a step of supplying fuel gas (LPG) to the ejector 123, a step of sucking outside air from the suction 121 of the ejector 123, a step of generating mixed gas of the fuel gas and air and injecting the mixed gas from the surface of the wick 127, a step of igniting the mixed gas injected from the wick 127 by the spark generated by the ignition plug (ignition device) 129 and burning the mixed gas within the combustor 105 and a step of discharging burnt air toward the vent 117 as warm air. This combustion state is continued until supply of LPG is stopped.

However, the ignition performance of the mixed gas and the combustion performance of the combustion gas after ignition are conflicting one another. That is, to improve the ignition performance of the gas, the ratio of the gas to air in the mixed gas needs to be increased, and however, when the mixed gas with high gas ratio is burnt, a large amount of incomplete combustion gas is generated and the combustion performance is lowered. As a result, CO concentration is increased.

Conversely, to improve the combustion efficiency, when the amount of air in the mixed gas is increased, thereby decreasing the ratio of gas in the mixed gas, the combustion performance is improved and however, it becomes difficult to set a fire because of much air, causing the problem that combustion cannot be started.

In the conventional gas combustion device, since combustion is performed in the state where a certain amount of air is supplied from the air blower 115 at all times, there is a problem that it is difficult to generate the mixed gas which fully satisfies both the ignition performance and the combustion performance.

To solve the above-mentioned problem, the present invention intends to provide a gas combustion control method and a gas combustion device capable of improving ignitability and combustion performance of gas and decreasing CO concentration.

DISCLOSURE OF THE INVENTION

To achieve the above-mentioned object, a gas combustion control method in a gas combustion device having a combustor for burning fuel gas supplied from a gas source, an air amount adjustment device for adjusting the amount of air in a cylindrical casing which contains the combustor therein, a wick for injecting mixed gas generated by mixing the fuel gas supplied from the gas source to the combustor and air in the casing into a combustion chamber, an ignition device for igniting the mixed gas injected from the wick, and a controller for controlling the air amount adjustment device and the ignition device, the method comprising the steps of: a first air amount adjustment step of controlling the air amount adjustment device so as to decrease the amount of air in the casing before the mixed gas injected from the wick is ignited, an ignition step of igniting the mixed gas, and a second air amount adjustment step of operating the air amount adjustment device at higher power than the first air amount adjustment step so as to increase the amount of air in the casing after the ignition step.

Moreover, to achieve the above-mentioned object, a gas combustion device comprises a combustor for burning fuel gas supplied from a gas source, an air amount adjustment device for adjusting the amount of air in a cylindrical casing which contains the combustor therein, a wick for injecting mixed gas generated by mixing the fuel gas supplied from the gas source to the combustor and air in the casing into a combustion chamber, an ignition device for igniting the mixed gas injected from the wick, an ignition detection device for detecting ignition of the mixed gas in the combustor and a controller for controlling at least the air amount adjustment device and the ignition device on the basis of a signal from the ignition detection device, and the controller controls the air amount adjustment device so as to decrease the amount of air in the casing when the ignition detection does not detect ignition and controls the air amount adjustment device so as to increase the amount of air in the casing when the ignition detection detects ignition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing combustion of gas in a conventional gas combustion device.

FIG. 2 is a side sectional view of a hair drier which contains the conventional gas combustion device therein.

FIG. 3 is a partial sectional view of an ejector in FIG. 2.

FIG. 4 is a front sectional view of a combustor taken along a line IV-IV in FIG. 2.

FIG. 5 is a schematic view showing combustion of gas in a gas combustion device in accordance with an embodiment of the present invention.

FIG. 6 is a side sectional view of the gas combustion device in accordance with the embodiment of the present invention taken along a line VI-VI in FIG. 7.

FIG. 7 is a front sectional view of the gas combustion device viewed from the left side in FIG. 6.

FIG. 8 is a back sectional view of the gas combustion device viewed from the right side in FIG. 6.

FIG. 9 is a flow chart showing a control method of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A gas combustion control method and a gas combustion device in accordance with an embodiment of the present invention will be described below with reference to drawings.

The case where a gas combustion device 1 in accordance with this embodiment is contained in a hair drier 3 will be described below. The hair drier 3 has a substantially cylindrical casing 5 and a long handle (not shown) is provided at a side wall face of the casing 5 in the direction substantially perpendicular to the longitudinal direction of the casing 5. The gas combustion device 1 is contained in the casing 5.

Referring to FIG. 6, the gas combustion device 1 has an ejector 7 for generating mixed gas consisting of LPG, for example, as fuel gas and air, an electrode 9 as an ignition device for igniting the mixed gas generated by the ejector 7 and a combustor 11 for burning the mixed gas ignited by the electrode 9.

An air blower 15 for flowing burnt air heated by the combustor 11 to the side of a vent 13 of the casing 5 is provided in the casing 5 in the rear of the ejector 7 (right side in FIG. 6).

The air blower 15 functions as an air amount adjustment device for adjusting the amount of air in the casing 5.

The air blower 15 is comprised of a direct-current motor 17 attached to the inner wall face in the rear of the casing 5 with a bracket 19 having an air passage and an axial-flow fan 21 for air blasting provided at a rotational shaft of the direct-current motor 17.

A rear end (right end in FIG. 6) of the casing 5 is covered with a wall having a lot of holes that performs as air intakes for safety reasons and a front end (left end in FIG. 6) of the casing 5 is detachably attached to a nozzle for hot air vent (not shown).

Referring to FIGS. 7 and 8, the combustor 11 will be described in more detail. A chamber 23 of the combustor 11 made of aluminum (die-cast) is a substantially cylindrical body with circular right and left side faces in the longitudinal direction of the chamber 11 in this embodiment as shown in FIGS. 7 and 8. The inside of the chamber 23 is comprised of a primary combustion chamber 25 located rearwards (right side in FIG. 6) and a secondary combustion chamber 27 located ahead of the primary combustion chamber 25 (left side in FIG. 6). The ejector 7 is attached to the gas induction side in the rear of the primary combustion chamber 25 (right side in FIG. 6)

The ejector 7 is provided with a nozzle 33 for injecting gas supplied from a gas source such as a gas tank (not shown) for storing fuel gas such as LPG through a gas supply pipe 31 as a gas passage at the side of an inlet of a substantially cylindrical ejector body 29 having a circular cross section. A pin hole as an injection hole (not shown) having a bore diameter of φ60 μm to φ200 μm, for example, is provided at a front end of the nozzle 33. The injection hole is an orifice formed substantially in the center of a disc-like pin-hole disc (not shown) and LPG is thinly discharged at high speed close to sonic speed. A filter (not shown) for removing impurities and dusts which block the injection hole is built in the nozzle 33. For example, a sintered metal with a pinhole having a diameter of 10 to 30 μm, for example, is used as the filter. The shape of the cross section of the ejector body may be changed as necessary.

A mixer 35 for mixing LPG with outside air (primary air) and introducing the mixed gas into the combustor 11 is provided in the ejector body 29 ahead of the nozzle 33 and a primary air hole 37 for sucking the primary air penetrates a side wall of the mixer 35. Accordingly, the pressure within the mixer 35 becomes negative due to the fuel gas discharged from the nozzle 33 at high speed, and the primary air is sucked from the outside and sent to a forward wick 39 as a gas combustion part while being mixed with the fuel gas. This is called as an ejector effect. By adjusting area of the primary air hole 37, the ratio of the primary air can be adjusted. As described later, the primary air supplied to the casing 5 per unit time is also adjusted by the output of the direct-current motor 17 controlled by a controller 55.

The wick 39 as a gas combustion part is a cylindrical SUS metal mesh of 50 to 150 mesh, for example, and is attached to the end ahead of the ejector body 29 by welding or the like substantially in the center of the right half of the primary combustion chamber 25 of the combustor 11 in FIG. 6. A wick holder 41 as a direct-advance suppression part is attached to the end ahead of the wick 39. The mixed gas discharged from the mixer 35 is guided mainly laterally (in the direction shown by an arrow ARI in FIG. 6) and the mixed gas of LPG and air is discharged from meshes of the wick 39. Flame after ignition is blue and substantially circular.

The electrode 9 is provided within the combustor 11 and ahead of the wick 39 and in the vicinity of the side face of the wick 39. High-tension electricity generated in a piezoelectric element for ignition (not shown) is input to the electrode 9 through an electric wire 43 and a spark is blown from the front end of the electrode 9 to the wick 39. The spark ignites the mixed gas discharged from the wick 39, thereby burning the gas.

Referring to FIG. 7, on an inner wall of the primary combustion chamber 25, a plurality of groove parts 45 extending in the forward-rearward direction are radially arranged around the wick 39. In FIG. 7, six groove parts 45 are formed.

A plurality of secondary air holes 46 for supplying outside air (secondary air) to the primary combustion chamber 25 are provided on a rear wall (right side wall in FIG. 6) of the primary combustion chamber 25. The plurality of secondary air holes 46 are disposed so that the secondary air is supplied to the gas after ignition at the position other than an ignition point. The ignition point means the area where a spark can blow at the side of the electrode 9 in the periphery of the wick 39 as shown by an area surrounded by a dotted line in FIG. 7. In this embodiment, five secondary air holes 46 are provided.

A plurality of tertiary air ducts 47 as tertiary air holes for supplying outside air (tertiary air) to the secondary combustion chamber 27 are provided in the wall of the primary combustion chamber 25 between adjacent groove parts 45. In this embodiment, six tertiary air ducts 47 in total are provided.

An opening is provided at a front end of the secondary combustion chamber 27. The opening forms a combustion gas vent 49 for discharging the combustion gas burnt in the secondary combustion chamber 27.

A plurality of fins 51 for heat exchange are provided at the outer periphery of the chamber 23. The fins 51 emits heat generated when the mixed gas is burnt in the chamber 23 and cool the chamber 23. Due to this effect of heat exchange, heat in the chamber 23 is emitted and the emitted heat is efficiently transmitted to air flow sent from the axial-flow fan 21.

An ignition detection device (ignition sensor) 53 for detecting ignition of the gas (LPG) in the combustor 11 is provided in the casing 5 (or handle) and in the vicinity of the combustion gas vent 49 of the combustor 11.

The controller 55 for controlling ON/OFF operation and rotational speed of the direct-current motor 17 according to a detection signal of detecting that the gas in the combustor 11 has been ignited by the ignition sensor 53 and controlling ON/OFF of conduction to the electrode 9 as an ignition device is provided in the casing 5.

In detail, the controller 55 performs different control depending on at ignition and after ignition. That is, at ignition, to decrease the amount of air in casing 5 for facilitating ignition, the controller 55 performs low-powered operation (Low operation) by decreasing the rotation rate of the direct-current motor 17. After ignition, based on the detection signal of ignition issued by the ignition sensor 53, the controller 55 performs high-powered operation (Hi operation) so as to increase the amount of air casing 5 to lower CO concentration by increasing the rotation rate of the direct-current motor 17. The controller 55 is electrically connected to a power source, the direct-current motor 17, the electrode 9 and the ignition sensor 53. Furthermore, the controller 55 controls the opening/closing operation of an open-and-close valve (not shown) for supplying and stopping the fuel gas.

Referring to FIG. 9, the operation of the controller 55 and procedure from operation to stoppage in this embodiment will be described below.

First, when an operating switch (not shown) is turned on (step 1), an ON signal is sent to the controller 55, a signal for energization is given from the controller 55 to the direct-current motor 17 of the air blower 15 and blowing is started (step 2). At the time of step 2, since LPG is not supplied to the combustor 11 and the ignition detection signal output by the ignition sensor 53 is OFF, a signal for decreasing the rotation rate of the direct-current motor 17 so as to decrease the amount of air in the casing 5 is given from the controller 55 and low-powered operation is performed (step 3). Subsequently, the open-and-close valve (not shown) of the gas supply pipe 31 is opened and LPG as fuel gas is supplied from the gas source to the nozzle 33 of the ejector 7 of the combustor 11 through the gas supply pipe 31 (step 4).

When LPG is supplied to the nozzle 33 of the ejector 7 through the gas supply pipe 31, LPG passes through the filter within the nozzle 33 and is injected from the injection hole as the orifice to the mixer 35 at a speed close to the sonic speed. For this reason, in the mixer 35, due to the negative pressure generated by the ejector effect, the primary air (corresponding to air-fuel ratio) necessary for combustion is sucked from the primary air hole 37 and flows into the mixer 35 (step 5). The inflow primary air at the step 5 and LPG are mixed to form mixed gas and the mixed gas in injected to the forward wick 39 (step 6).

At the step 6, in proportion to increase and decrease in LPG, the primary air necessary for combustion is automatically sucked into the mixer 35. However, in the casing 5, since the direct-current motor 17 is operated at low power by the controller 55, the amount of air for combustion at ignition is decreased and therefore, as shown by a small arrow in FIG. 5, the amount of the primary air sucked from the primary air hole 37 is also decreased. For this reason, the mixed gas with good ignitability because of the high gas ratio is injected to the forward wick 39.

Since the wick holder 41 is provided at a forward end face of the wick 39, the mixed gas is injected to the periphery mainly from the side SUS metal mesh.

Subsequently, in response to an instruction from the controller 55, high-tension electricity generated by the ignition piezoelectric device is passed through the electric wire 43, and a spark is generated from the electrode 9 in the combustor 11 and ignites the mixed gas with good ignitability injected from the wick 39.

Timing of ignition, that is, the time from completion of the step 6 to execution of the step 7, is changed as necessary depending on the apparatus to which the present invention applies. In other words, ignition timing most suited to each apparatus is determined in consideration of volume of the casing 5 and the like.

Most of burning flame of the ignited gas spreads outwards in a circle pattern from the side face of the wick 39 and the length of the burning flame remains to be ten-odd mm from the wick 39. Warm air is transmitted along the inside of the primary combustion chamber 25 and six groove parts 31 on the inner wall to the forward secondary combustion chamber 25.

Next, ON/OFF of the ignition signal is determined (step 8). When the combustion gas is discharged from the combustion gas vent 49 ahead of the secondary combustion chamber 27, the ignition sensor 53 provided in the vicinity of the combustion gas vent 49 detects that the gas in the combustor 11 is ignited and burnt (YES at the step 8). By sending this ignition detection signal to the controller 55, high-powered operation is started according to the instruction from the controller 55 (step 9) and the rotation rate of the direct-current motor 17 is increased, so that the amount of air in the casing 5 is increased. When the ignition detection signal is not in the ON state at the step 8, that is, ignition is not started, the operation returns to the step 7.

When high-powered operation is started, the amount of the primary air sucked from the primary air hole 37 as air for combustion during combustion is increased as shown by a large arrow in FIG. 5. For this reason, the ration of air in the mixed gas in the mixer 35 is increased, the mixed gas with good combustibility is injected from the wick 39 and the combustion response of the gas in the primary combustion chamber 25 is promoted, thereby improving the combustion performance.

Further, in the primary combustion chamber 25, to improve the combustion efficiency by increasing the amount of air in the casing 5, the secondary air is introduced through the five secondary air holes 46 (step 10). As a result, the combustion response of the gas in the primary combustion chamber 25 is promoted, thereby further improving the combustion performance.

Furthermore, in the secondary combustion chamber 27, the tertiary air is introduced through six tertiary air ducts (tertiary air holes) 47 (step 11). The tertiary air efficiently decreases the temperature of a wall part of the primary combustion chamber 25 and is heated up to high temperature when passing through the tertiary air ducts 47 and introduced into the secondary combustion chamber 27. As a result, the combustion response of the gas in the primary combustion chamber 25 is promoted, thereby further improving the combustion performance. That is, since the gas burnt in the primary combustion chamber 25 and the hot tertiary air, the amount of which is increased, are mixed, the combustion response easily occurs and complete combustion is facilitated, thereby improving the combustion performance and decreasing CO concentration.

On the other hand, when the operating switch is turned off (step 12), the direct-current motor 17 is stopped by the controller 55 and the open-and-close valve (not shown) of the gas supply pipe 31 is blocked (step 13). As a result, a supply path is blocked and the operation of the combustion gas device is stopped.

The present invention is not limited to the above-mentioned embodiments and can be carried out according to the other aspects. The gas combustion device in accordance with this embodiment can be used as the gas combustion device such as a hair drier and a heat gun used for compression operation of a heat-shrinkable tube, drying, adhesion, fusing and soldering and the other gas combustion devices such as the other appliances.

INDUSTRIAL APPLICABILITY

According to the present invention, at ignition, by decreasing the amount of air in the casing, the amount of air sucked from the ejector is decreased and thus the amount of air in the mixed gas is decreased, thereby increasing the gas ratio. As a result, ignitability of the mixed gas emitted from the wick can be improved. After ignition, by increasing the amount of air in the casing, the combustion efficiency of the combustion gas in the combustor and the combustion performance can be improved, thereby decreasing CO concentration.

Further, according to the present invention, by the simple method of merely switching power of the air blower to high power or low power, the ignition performance at ignition and the combustion performance after ignition can be improved.

Furthermore, according to the present invention, at ignition, by decreasing the amount of air in the casing, the amount of air sucked from the ejector is decreased and thus the amount of air in the mixed gas is decreased, thereby increasing the gas ratio. As a result, ignitability of the mixed gas emitted from the wick can be improved. After ignition, by increasing the amount of air in the casing, the combustion efficiency of the combustion gas in the combustor and the combustion performance can be improved, thereby decreasing CO concentration. 

1. A gas combustion control method in a gas combustion device having a combustor for burning fuel gas supplied from a gas source; an air amount adjustment device for adjusting the amount of air in a cylindrical casing which contains the combustor therein; a wick for injecting mixed gas generated by mixing the fuel gas supplied from the gas source to the combustor and air in the casing into a combustion chamber; an ignition device for igniting the mixed gas injected from the wick; and a controller for controlling the air amount adjustment device and the ignition device, comprising the steps of: a first air amount adjustment step of controlling the air amount adjustment device so as to decrease the amount of air in the casing before the mixed gas injected from the wick is ignited; an ignition step of igniting the mixed gas; and a second air amount adjustment step of operating the air amount adjustment device at higher power than the first air amount adjustment step so as to increase the amount of air in the casing after the ignition step.
 2. A gas combustion control method of claim 1, wherein the air amount adjustment device further comprises an air blower for flowing the air heated by the combustor to the side of a vent of the casing, and in the first amount adjustment step, the controller decreases the amount of air blast of the air blower, and in the second amount adjustment step, the controller increases the amount of air blast of the air blower.
 3. A gas combustion device comprising: a combustor for burning fuel gas supplied from a gas source; an air amount adjustment device for adjusting the amount of air in a cylindrical casing which contains the combustor therein; a wick for injecting mixed gas generated by mixing the fuel gas supplied from the gas source to the combustor and air in the casing into a combustion chamber; an ignition device for igniting the mixed gas injected from the wick; an ignition detection device for detecting ignition of the mixed gas in the combustor and a controller for controlling at least the air amount adjustment device and the ignition device on the basis of a signal from the ignition detection device, wherein the controller controls the air amount adjustment device so as to decrease the amount of air in the casing when the ignition detection does not detect ignition and controls the air amount adjustment device so as to increase the amount of air in the casing when the ignition detection detects ignition.
 4. A gas combustion device of claim 3, wherein the air amount adjustment device has an air blower for flowing the air heated by the combustor to the side of a vent of the casing.
 5. A gas combustion device of claim 3 further comprising: a first suction port for sucking outside air to be mixed with the gas before the ignition detection device detects ignition, and a second suction port and a third suction port for sucking outside air by the air amount adjustment device after the ignition detection device detects ignition.
 6. A gas combustion device of claim 3 further comprising an open-and-close valve which opens or closes a supply pipe for supplying the gas to the combustor, wherein the controller controls the open-and-close valve.
 7. A gas combustion control method in a gas combustion device having a combustor for burning fuel gas supplied from a gas source; an air amount adjustment device for adjusting the amount of air in a cylindrical casing which contains the combustor therein; a wick for injecting mixed gas generated by mixing the fuel gas supplied from the gas source to the combustor and air in the casing into a combustion chamber; an ignition device for igniting the mixed gas injected from the wick; an ignition detection device for detecting ignition of the mixed gas in the combustor; an open-and-close valve for supplying the fuel gas into the combustor; and a controller for controlling the air amount adjustment device and the ignition device, comprising the steps of: operating the air amount adjustment device at low power and blowing air into the casing; opening the open-and-close valve to supply the fuel gas; mixing a primary air sucked in the casing and the fuel gas to generate the mixed gas; injecting the mixed gas; igniting the mixed gas by the ignition device; operating the air amount adjustment device at high power when the ignition detection device detects ignition; sucking a secondary air into the casing; and sucking a tertiary air into the casing. 